Possible Duplicate:
Can't boot without Flash Drive plugged in
My problem is very much like the problem described in the link.
I have FreeDOS and Ubuntu 12.04. When I boot without bootable USB the computer simply proceeds to DOS. With USB stick I have to enter ubuntu via BIOS.
I WISH TO REINSTALL Ubuntu. What is the procedure to reinstall ubuntu from ubuntu itself?
Or is there any other solution to the problem?
You will find a guide here: How to Install Ubuntu 12.04 Precise Pangolin
Take care: at a certain moment the system will ask you where the bootloader must be installed. Not in the usb of course, but mostly on your hard disk (C drive) - sad1 (mostly).
sudo grub-install /dev/sda && sudo update-grub
Running this code in the terminal solves the problem.
Thanks a lot to Adempewolff.